Freezing rain advisory for D.C. area early Friday

Area covered by freezing rain advisory (National Weather Service)

Area covered by freezing rain advisory (National Weather Service)

When what’s left of the polar vortex air mass joins forces with a warm front coming in from the south, some light freezing rain is possible late tonight into Friday morning.

The National Weather Service has issued a freezing rain advisory for much of the region Friday morning – from 3 a.m. to 9 a.m. Calvert and St. Mary’s counties in southern Maryland are excluded, as temperatures there are expected to quickly rise above freezing.

Generally, a glaze of less 0.1″ is expected, but that’s all that’s required to cause slick conditions given the cold ground, especially on untreated sidewalks and roads.

Also, this event will coincide with rush hour, increasing its impact, especially through around 7 or 8 a.m.

“The precipitation may start briefly as snow or sleet before transitioning to freezing rain during the morning and eventually rain during the day on Friday,” says CWG’s winter weather expert Wes Junker. “Like most of these messy freezing rain type events, the freezing rain is likely to hang in longer the further west you get from the city. By mid-morning most locations in and around the city should rise to above freezing. Out towards the colder locations near the mountains the light freezing rain could hold on a little longer.”

High resolution NAM model simulated radar shows light precipitation in the region with temperatures generally at or below 32 in the region (blue line) at 7 a.m. (WeatherBell.com)

High resolution NAM model simulated radar shows light precipitation  with temperatures generally at or below 32 in the region (blue line) at 7 a.m. (WeatherBell.com)

This is a very marginal event for areas near and east of I-95. Locations close to and inside the District may be just warm enough to avoid major problems – with temperatures perhaps in the range of 31-34 degrees. By 9  a.m. most places within a one county radius of the District should be above freezing with just plain rain.

But if you live in western Fairfax and Montgomery county and particularly Loudoun and Frederick counties, temperatures in the upper 20s to near 30 pose the risk of more significant icing and impacts on roads, and a longer duration of iciness.

High resolution NAM model simulated radar shows light to moderate precipitation over the region at 9 a.m., but the freezing line has mostly lifted north into Pennsylvania. Sometimes such models warm temperatures too quickly, however, especially in D.C.'s colder suburbs. (WeatherBell.com)

High resolution NAM model simulated radar shows light to moderate precipitation over the region at 9 a.m., but the freezing line (in blue) has mostly lifted north into Pennsylvania. Sometimes such models warm temperatures too quickly, however, especially in D.C.’s colder suburbs. (WeatherBell.com)

Some colder pockets of Loudoun and Frederick counties may stay below freezing into the afternoon hours. But this event should not be a repeat of Sunday as there should be a stronger push of warm air from the south to scour out the cold everywhere, eventually.

SchoolCast

Loudoun and Frederick Counties

(Two apples: good chance of delay, 50/50 chance no school)

St. Mary’s and Calvert counties

1_apple

(1 apple: school likely on time)

Everywhere else

1.5_apple

(1.5 apples: 50/50 chance of a delay)

FedCast

capitol-black.jpg

(1 dome: expect to report to work on time)

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